Millimeter-wave stealth radio for special operations forces

For Special Operations Forces, an important attribute of any future radio will be the ability to conceal transmissions from the enemy while transmitting large amounts of data for situational awareness and communications. These requirements will mean that military wireless systems designers will need to consider operating frequencies in the mm-wave bands: The high data rates that are achievable at these frequencies and the propagation characteristics at this wavelength will provide many benefits for the implementation of 'stealth radio'. This article discusses some of the recent advances in RF front-end technology, alongside physical layer transmission schemes that could be employed for millimeter-wave soldier-mounted radio. The operation of a hypothetical millimeter-wave soldier-to-soldier communications system that makes use of smart antenna technology is also described.

Millimetre-wave broadband wireless systems and enabling MMIC technologies

Chapter eleven on Mm-wave broadband wireless systems and enabling MMIC technologies, is contributed by Jian Zhang, Mury Thian, Guochi Huang, George Goussetis and Vincent F. Fusco, from Queen's University Belfast, UK. Millimeter wave bands provide large available bandwidths for high data rate wireless communication systems, which are envisaged to shift data throughput well in the GBps range. This capability has over past few years driven rapid developments in the technology underpinning broadband wireless systems as well as in the standardisation activity from various non-governmental consortia and the band allocation from spectrum regulators globally. This chapter provides an overview of the recent developments on V-band broadband wireless systems with the emphasis placed on enabling MMIC technologies. An overview of the key applications and available standards is presented. System-level architectures for broadband wireless applications are being reviewed. Examples of analysis, design and testing on MMIC components in SiGe BiCMOS are presented and the outlook of the technology is discussed.

On the nature of ULF wave power during nightside auroral activations and substorms: 2. temporal evolution

We present a statistical analysis of the time evolution of ground magnetic fluctuations in three (12–48 s, 24–96 s and 48–192 s) period bands during nightside auroral activations. We use an independently derived auroral activation list composed of both substorms and pseudo-breakups to provide an estimate of the activation times of nightside aurora during periods with comprehensive ground magnetometer coverage. One hundred eighty-one events in total are studied to demonstrate the statistical nature of the time evolution of magnetic wave power during the ∼30 min surrounding auroral activations. We find that the magnetic wave power is approximately constant before an auroral activation, starts to grow up to 90 s prior to the optical onset time, maximizes a few minutes after the auroral activation, then decays slightly to a new, and higher, constant level. Importantly, magnetic ULF wave power always remains elevated after an auroral activation, whether it is a substorm or a pseudo-breakup. We subsequently divide the auroral activation list into events that formed part of ongoing auroral activity and events that had little preceding geomagnetic activity. We find that the evolution of wave power in the ∼10–200 s period band essentially behaves in the same manner through auroral onset, regardless of event type. The absolute power across ULF wave bands, however, displays a power law-like dependency throughout a 30 min period centered on auroral onset time. We also find evidence of a secondary maximum in wave power at high latitudes ∼10 min following isolated substorm activations. Most significantly, we demonstrate that magnetic wave power levels persist after auroral activations for ∼10 min, which is consistent with recent findings of wave-driven auroral precipitation during substorms. This suggests that magnetic wave power and auroral particle precipitation are intimately linked and key components of the substorm onset process.

Space-Time Scales of Northward Propagation of Convection during Boreal Summer

This study uses precipitation estimates from the Tropical Rainfall Measuring Mission to quantify the spatial and temporal scales of northward propagation of convection over the Indian monsoon region during boreal summer. Propagating modes of convective systems in the intraseasonal time scales such as the Madden-Julian oscillation can interact with the intertropical convergence zone and bring active and break spells of the Indian summer monsoon. Wavelet analysis was used to quantify the spatial extent (scale) and center of these propagating convective bands, as well as the time period associated with different spatial scales. Results presented here suggest that during a good monsoon year the spatial scale of this oscillation is about 30 degrees centered around 10 degrees N. During weak monsoon years, the scale of propagation decreases and the center shifts farther south closer to the equator. A strong linear relationship is obtained between the center/scale of convective wave bands and intensity of monsoon precipitation over Indian land on the interannual time scale. Moreover, the spatial scale and its center during the break monsoon were found to be similar to an overall weak monsoon year. Based on this analysis, a new index is proposed to quantify the spatial scales associated with propagating convective bands. This automated wavelet-based technique developed here can be used to study meridional propagation of convection in a large volume of datasets from observations and model simulations. The information so obtained can be related to the interannual and intraseasonal variation of Indian monsoon precipitation.

SiO2 对Bi2O3-B2O3 玻璃体系光学、热学及结构的 影响

Glasses with compositions 50Bi2O3-xB2O3- (50-x)SiO2(x=0, 10, 20, 30, 40, 50) in mol% have been prepared by using a normal melt-quench technique. The effect of SiO2 addition on thermal stability, optical properties and structural characteristic on Bi2O3-B2O3 glass were systematically investigated by using XRD, DTA, ultraviolet-visible transmittance spectra, midinfrared transmittance spectra and Raman spectra. The experimental results demonstrate that, with the addition of SiO2, thermal stability of glass samples has been obviously improved. Once the amount of SiO2 is too much, the glass samples tend to be phase seperation which results in the decrease of thermal stability. With increasing SiO2 content, the UV cutoff edge firstly shifts to short-wave band and then shifts to long-wave band, and the transmittance of mid-infrared has been greatly improved. With substitution of SiO2 for B2O3, the [BO3] triangles and [BO4] tetrahedral groups are gradually replaced by [SiO4]. [BiO6] octahedral and [SiO4] tetrahedral units are connected forming a vibrational mode of Bi-O-Si. The physical chemistry and optical performance of Bi2O3-B2O3 glass were greatly improved by addition of SiO2.

Propagating waves and magnetohydrodynamic mode coupling in the quiet-sun network

High-cadence multiwavelength optical observations were taken with the Dunn Solar Telescope at the National Solar Observatory, Sacramento Peak, accompanied by Advanced Stokes Polarimeter vector magnetograms. A total of 11 network bright points (NBPs) have been studied at different atmospheric heights using images taken in wave bands centered on Mg I b(1) - 0.4 Angstrom, Halpha, and Ca II K-3. Wavelet analysis was used to study wave packets and identify traveling magnetohydrodynamic waves. Wave speeds were estimated through the temporal cross-correlation of signals, in selected frequency bands of wavelet power, in each wavelength. Four mode-coupling cases were identified, one in each of four of the NBPs, and the variation of the associated Fourier power with height was studied. Three of the detected mode-coupling, transverse-mode frequencies were observed in the 1.2-1.6 mHz range (mean NBP apparent flux density magnitudes over 99-111 Mx cm(-2)), with the final case showing 2.0-2.2 mHz (with 142 Mx cm(-2)). Following this, longitudinal-mode frequencies were detected in the range 2.6-3.2 mHz for three of our cases, with 3.9-4.1 mHz for the remaining case. After mode coupling, two cases displayed a decrease in longitudinal-mode Fourier power in the higher chromosphere.

Electronic Circuit Packages

This invention relates to electronic circuit packages designed to hold high frequency circuits operating particularly, but not exclusively, in the microwave, millimeter wave, and sub-millimeter wave bands. The invention provides a package incorporating a cavity in a material for containment of the circuits, wherein the package further incorporates at least one conductive surface mounted on an inner surface extending into the cavity, the conductivity thereof being adapted to be at least partially absorbent to electromagnetic radiation. The conductive surface according to the present invention will tend to attenuate electromagnetic radiation present within the cavity, and so help to prevent undesired coupling from one point to another within the cavity. The conductivity of the conductive material is preferably arranged to match the impedance of the radiation mode estimated or computed to be present within the cavity.

Normal type Ia supernovae from violent mergers of white dwarf binaries

One of the most important questions regarding the progenitor systems of Type Ia supernovae (SNe Ia) is whether mergers of two white dwarfs can lead to explosions that reproduce observations of normal events. Here we present a fully three-dimensional simulation of a violent merger of two carbon-oxygen white dwarfs with masses of 0.9 M and 1.1 M combining very high resolution and exact initial conditions. A well-tested combination of codes is used to study the system. We start with the dynamical inspiral phase and follow the subsequent thermonuclear explosion under the plausible assumption that a detonation forms in the process of merging. We then perform detailed nucleosynthesis calculations and radiative transfer simulations to predict synthetic observables from the homologously expanding supernova ejecta. We find that synthetic color light curves of our merger, which produces about 0.62 M of Ni, show good agreement with those observed for normal SNe Ia in all wave bands from U to K. Line velocities in synthetic spectra around maximum light also agree well with observations. We conclude that violent mergers of massive white dwarfs can closely resemble normal SNe Ia. Therefore, depending on the number of such massive systems available these mergers may contribute at least a small fraction to the observed population of normal SNe Ia. © 2012 The American Astronomical Society. All rights reserved.

Fourier transform infrared microspectroscopy as a tool to identify macroalgal propagules

Understanding of macroalgal dispersal has been hindered by the difficulty in identifying propagules. Different carrageenans typically occur in gametophytes and tetrasporophytes of the red algal family Gigartinaceae, and we may expect that carpospores and tetraspores also differ in composition of carrageenans. Using Fourier transform infrared (FT-IR) microspectroscopy, we tested the model that differences in carrageenans and other cellular constituents between nuclear phases should allow us to discriminate carpospores and tetraspores of Chondrus verrucosus Mikami. Spectral data suggest that carposporophytes isolated from the pericarp and female gametophytes contained κ-carrageenan, whereas tetrasporophytes contained λ-carrageenan. However, both carpospores and tetraspores exhibited absorbances in wave bands characteristic of κ-,ι-, and λ-carrageenans. Carpospores contained more proteins and may be more photosynthetically active than tetraspores, which contained more lipid reserves. We draw analogies to planktotrophic and lecithotrophic larvae. These differences in cellular chemistry allowed reliable discrimination of spores, but pretreatment of spectral data affected the accuracy of classification. The best classification of spores was achieved with extended multiplicative signal correction (EMSC) pretreatment using partial least squares discrimination analysis, with correct classification of 86% of carpospores and 83% of tetraspores. Classification may be further improved by using synchrotron FT-IR microspectroscopy because of its inherently higher signal-to-noise ratio compared with microspectroscopy using conventional sources of IR. This study demonstrates that FT-IR microspectroscopy and bioinformatics are useful tools to advance our understanding of algal dispersal ecology through discrimination of morphologically similar propagules both within and potentially between species.

Acoplador e linha de lâmina unilateral e bilateral com substrato fotônico

The aim of this work is to characterize and use the characteristic parameters of the planar structures constructed with fin lines looking for their applications in devices, using PBG Photonic Band Gap photonic materials as substrate, operating in the millimeter and optic wave bands.The PBG theory will be applied for the relative permittivity attainment for the PBG photonic substrate s and p polarizations. The parameters considered in the structures characterization are the complex propagation constant and the characteristic impedance of unilateral and bilateral fin lines that were obtained by the use of the TTL Transverse Transmission Line Method, together with the Method of the Moments. The final part of this work comprises studies related to the behavior of the asymmetric unilateral fin line coupler with photonic substrate. This research opens perspectives for new works in this modern area. Numerical results are shown by means of bi-dimensional and three-dimensional graphics. Conclusions and suggestions for future works are also presented

Desarrollo y aplicaciones de radares de alta resolución en bandas milimétricas

Las bandas de las denominadas ondas milimétricas y submilimétricas están situadas en la región del espectro entre las microondas y el infrarrojo. La banda de milimétricas se sitúa entre 30 y 300 GHz, considerada normalmente como la banda EHF (Extremely High Frequency). El margen de frecuencias entre 300 y 3000 GHz es conocido como la banda de ondas submilimétricas o de terahercios (THz). Sin embargo, no toda la comunidad científica está de acuerdo acerca de las frecuencias que limitan la banda de THz. De hecho, 100 GHz y 10 THz son considerados comúnmente como los límites inferior y superior de dicha banda, respectivamente. Hasta hace relativamente pocos años, la banda de THz sólo había sido explotada para aplicaciones en los campos de la espectroscopía y la radioastronomía. Los avances tecnológicos en la electrónica de microondas y la óptica lastraron el desarrollo de la banda de THz. Sin embargo, investigaciones recientes han demostrado las ventajas asociadas a operar en estas longitudes de onda, lo que ha aumentado el interés y los esfuerzos dedicados a la tecnología de THz. A pesar de que han surgido un gran número de aplicaciones, una de las más prometedoras está en el campo de la vigilancia y la seguridad. Esta tesis está dedicada al desarrollo de radares de onda continua y frecuencia modulada (CW-LFM) de alta resolución en la banda de milimétricas, más concretamente, en las ventanas de atenuación situadas en 100 y 300 GHz. Trabajar en estas bandas de frecuencia presenta beneficios tales como la capacidad de las ondas de atravesar ciertos materiales como la ropa o el papel, opacos en el rango visible, y la posibilidad de usar grandes anchos de banda, obteniéndose así elevadas resoluciones en distancia. Los anchos de banda de 9 y 27 GHz seleccionados para los sistemas de 100 y 300 GHz, respectivamente, proporcionan resoluciones en distancia alrededor y por debajo del cm. Por otro lado, las aplicaciones objetivo se centran en la adquisición de imágenes a corto alcance. En el caso del prototipo a 300 GHz, su diseño se ha orientado a aplicaciones de detección a distancia en escenarios de vigilancia y seguridad. La naturaleza no ionizante de esta radiación supone una ventaja frente a las alternativas tradicionalmente usadas tales como los sistemas de rayos X. La presente tesis se centra en el proceso de diseño, implementación y caracterización de ambos sistemas así como de la validación de su funcionamiento. Se ha elegido una solución basada en componentes electrónicos, y no ópticos, debido a su alta fiabilidad, volumen reducido y amplia disponibilidad de componentes comerciales. Durante el proceso de diseño e implementación, se han tenido en cuenta varias directrices tales como la minimización del coste y la versatilidad de los sistemas desarrollados para hacer posible su aplicación para múltiples propósitos. Ambos sistemas se han utilizado en diferentes pruebas experimentales, obteniendo resultados satisfactorios. Aunque son sólo ejemplos dentro del amplio rango de posibles aplicaciones, la adquisición de imágenes ISAR de modelos de blancos a escala para detección automática así como la obtención de datos micro-Range/micro- Doppler para el análisis de patrones humanos han validado el funcionamiento del sistema a 100 GHz. Por otro lado, varios ejemplos de imágenes 3D obtenidas a 300 GHz han demostrado las capacidades del sistema para su uso en tareas de seguridad y detección a distancia. ABSTRACT The millimeter- and submillimeter-wave bands are the regions of the spectrum between the microwaves and the infrared (IR). The millimeter-wave band covers the range of the spectrum from 30 to 300 GHz, which is usually considered as the extremely high frequency (EHF) band. The range of frequencies between 300 and 3000 GHz is known as the submillimeter-wave or terahertz (THz) band. Nevertheless, the boundaries of the THz band are not accepted by the whole research community. In fact, 100 GHz and 10 THz are often considered by some authors as the lower and upper limit of this band, respectively. Until recently, the THz band had not been exploited for practical applications, with the exception of minor uses in the fields of spectroscopy and radio astronomy. The advancements on microwave electronics and optical technology left the well-known THz gap undeveloped. However, recent research has unveiled the advantages of working at these frequencies, which has motivated the increase in research effort devoted to THz technology. Even though the range of upcoming applications is wide, the most promising ones are in the field of security and surveillance. Particularly, this Ph.D. thesis deals with the development of high resolution continuouswave linear-frequency modulated (CW-LFM) radars in the millimeter-wave band, namely, in the attenuation windows located at 100 and 300 GHz. Working at these wavelengths presents several benefits such as the ability of radiation to penetrate certain materials, visibly opaque, and the great availability of bandwidth at these frequencies, which leads to high range resolution. The selected bandwidths of 9 and 27 GHz for these systems at 100 and 300 GHz, respectively, result in cm and sub-cm range resolution. On the other hand, the intended applications are in the field of short-range imaging. In particular, the design of the 300-GHz prototype is oriented to standoff detection for security and surveillance scenarios. The non-ionizing nature of this radiation allows safety concerns to be alleviated, in clear contrast to other traditional alternatives such as X-rays systems. This thesis is focused on the design, implementation and characterization process of both systems as well as the experimental assessment of their performances. An electronic approach has been selected instead of an optical solution so as to take advantage of its high reliability, reduced volume and the availability of commercial components. Through the whole design and implementation process, several guidelines such as low cost and hardware versatility have been also kept in mind. Taking advantage of that versatility, different applications can be carried out with the same hardware concept. Both radar systems have been used in several experimental trials with satisfactory results. Despite being mere examples within the wide range of fields of application, ISAR imaging of scaled model targets for automatic target recognition and micro-Range/micro-Doppler analysis of human patterns have validated the system performance at 100 GHz. In addition, 3D imaging examples at 300 GHz demonstrate the radar system’s capabilities for standoff detection and security tasks.

Quantum fluctuations stabilize skyrmion textures

We study the quantum spin waves associated to skyrmion textures. We show that the zero-point energy associated to the quantum spin fluctuations of a noncollinear spin texture produce Casimir-like magnetic fields. We study the effect of these Casimir fields on the topologically protected noncollinear spin textures known as skyrmions. In a Heisenberg model with Dzyalonshinkii-Moriya interactions, chosen so the classical ground state displays skyrmion textures, we calculate the spin-wave spectrum, using the Holstein-Primakoff approximation, and the associated zero-point energy, to the lowest order in the spin-wave expansion. Our calculations are done both for the single-skyrmion case, for which we obtain a discrete set of skyrmion bound states, as well as for the skyrmion crystal, for which the resulting spectrum gives the spin-wave bands. In both cases, our calculations show that the Casimir magnetic field contributes up to 10% of the total Zeeman energy necessary to delete the skyrmion texture with an applied field.

Topological spin waves in the atomic-scale magnetic skyrmion crystal

We study the spin waves of the triangular skyrmion crystal that emerges in a two-dimensional spin lattice model as a result of the competition between Heisenberg exchange, Dzyalonshinkii–Moriya interactions, Zeeman coupling and uniaxial anisotropy. The calculated spin wave bands have a finite Berry curvature that, in some cases, leads to non-zero Chern numbers, making this system topologically distinct from conventional magnonic systems. We compute the edge spin-waves, expected from the bulk-boundary correspondence principle, and show that they are chiral, which makes them immune to elastic backscattering. Our results illustrate how topological phases can occur in self-generated emergent superlattices at the mesoscale.